Function ɵɵrepeater

packages/core/src/render3/instructions/control_flow.ts:504–592

(collection: Iterable<unknown> | undefined | null)

 * @codeGenApi
 */
export function ɵɵrepeater(collection: Iterable<unknown> | undefined | null): void {
  const prevConsumer = setActiveConsumer(null);
  const metadataSlotIdx = getSelectedIndex();
  try {
    const hostLView = getLView();
    const hostTView = hostLView[TVIEW];
    const metadata = hostLView[metadataSlotIdx] as RepeaterMetadata;
    const containerIndex = metadataSlotIdx + 1;
    const lContainer = getLContainer(hostLView, containerIndex);

    if (metadata.liveCollection === undefined) {
      const itemTemplateTNode = getExistingTNode(hostTView, containerIndex);
      metadata.liveCollection = new LiveCollectionLContainerImpl(
        lContainer,
        hostLView,
        itemTemplateTNode,
      );
    } else {
      metadata.liveCollection.reset();
    }

    const liveCollection = metadata.liveCollection;
    reconcile(liveCollection, collection, metadata.trackByFn, prevConsumer);

    // Warn developers about situations where the entire collection was re-created as part of the
    // reconciliation pass. Note that this warning might be "overreacting" and report cases where
    // the collection re-creation is the intended behavior. Still, the assumption is that most of
    // the time it is undesired.
    if (
      ngDevMode &&
      metadata.trackByFn === ɵɵrepeaterTrackByIdentity &&
      liveCollection.operationsCounter?.wasReCreated(liveCollection.length) &&
      isViewExpensiveToRecreate(getExistingLViewFromLContainer(lContainer, 0))
    ) {
      const message = formatRuntimeError(
        RuntimeErrorCode.LOOP_TRACK_RECREATE,
        `The configured tracking expression (track by identity) caused re-creation of the entire collection of size ${liveCollection.length}. ` +
          'This is an expensive operation requiring destruction and subsequent creation of DOM nodes, directives, components etc. ' +
          'Please review the "track expression" and make sure that it uniquely identifies items in a collection.',
      );
      console.warn(message);
    }

    // moves in the container might caused context's index to get out of order, re-adjust if needed
    liveCollection.updateIndexes();

    // handle empty blocks
    if (metadata.hasEmptyBlock) {
      const bindingIndex = nextBindingIndex();
      const isCollectionEmpty = liveCollection.length === 0;
      if (bindingUpdated(hostLView, bindingIndex, isCollectionEmpty)) {
        const emptyTemplateIndex = metadataSlotIdx + 2;
        const lContainerForEmpty = getLContainer(hostLView, emptyTemplateIndex);
        if (isCollectionEmpty) {
          const emptyTemplateTNode = getExistingTNode(hostTView, emptyTemplateIndex);
          const dehydratedView = findAndReconcileMatchingDehydratedViews(
            lContainerForEmpty,
            emptyTemplateTNode,